The man who murdered President Hamid Karzai’s half brother spent years as an ally of the United States in the war against the Taliban.

The killer, Sardar Mohammad, a police commander, met on several occasions with U.S. and British military officials, shared intelligence with Americans and played a part in Afghan arrests of scores of Taliban fighters, according to three relatives interviewed on Thursday in his home near Kandahar.

The reasons behind the dramatic switch that turned the 35-year-old officer against Ahmed Wali Karzai, perhaps the most powerful figure in southern Afghanistan, are still not understood. But one of Karzai’s brothers and a senior Afghan official said they were now convinced that the Taliban somehow won Mohammad’s allegiance in recent months and convinced him to carry out an assassination on the group’s behalf.

The official said that investigators are trying to determine whether Mohammad was a long-term Taliban sleeper agent or just recently joined the insurgents. A NATO spokesman in Afghanistan referred questions about Karzai’s killing to Afghan authorities. 

Mahmood Karzai, one of the president’s brothers, said the family has learned since the assassination that Mohammad traveled to the Pakistani city of Quetta within the past three months to meet with Taliban insurgents. He had also acted erratically in recent weeks, sleeping poorly, changing houses at night, acting suspiciously toward his men and demanding to know who they were talking to on their phones.

“All of a sudden, he changed,” Mahmood Karzai said in an interview Thursday. “This is the work of the Taliban.”

The senior Afghan official, interviewed separately, said he had heard about the Quetta visit but could not confirm its accuracy. He said Mohammad had attended a Pakistani madrassa in his youth before returning to Afghanistan. The senior official said that “the Taliban and the forces behind Taliban’’ were responsible for the killing.

The Taliban has claimed responsibility for the killing, and if it was indeed the group’s work, it would be one more example of the insurgents’ ability to attack even the most closely guarded targets. On Thursday, a man hid a bomb in his turban and killed four people at Ahmed Wali Karzai’s memorial service.

At Mohammad’s home, a relatively spacious concrete dwelling protected by military-style barriers — in a poor village of ancient-looking mud hovels — the police commander’s relatives adamantly denied that he would have worked on behalf of the Taliban. One of his brothers-in-law, Abdul Malik, said that Mohammad had not been in Pakistan for 20 years. On the walls of the sitting room are large photographs of Ahmed Wali Karzai and President Hamid Karzai, men he was devoted to, said his relatives.

“We were just like one family,” said one relative who declined to be named. “Until today, there wasn’t any dispute between us.”

A long history

Mohammad had known the Karzai family for many years and began working with Ahmed Wali Karzai, the leader of Kandahar’s provincial council, after the fall of the Taliban. Mohammad had been opposed to the Taliban’s regime because his village’s close proximity to the Karzai family’s ancestral home village down the road led the Taliban to harass them, according to relatives.

With Karzai’s help, Mohammad, who had been a melon farmer with a wife, three sons and four daughters, eventually became a police commander responsible for about 200 men who guarded eight checkpoints, the relatives said. Among his duties were to guard Karzai family homes and the cemetery where Ahmed Wali Karzai was buried on Wednesday.

He met six days a week with Ahmed Wali Karzai, who would pay his policemen’s salary if it was late and also provide additional money for him, Malik said. Their relationship was so close that Karzai brought his mother to Mohammad’s home. And just days before his death, Karzai asked the government for more equipment and personnel for Mohammad, according to the senior Afghan official.

Mohammad also met with U.S. and British military officials, and would be introduced to the new commanders when they rotated into Kandahar, the relatives said. Two of Mohammad’s brothers-in-law said they work as guards at a Central Intelligence Agency base in Kandahar — situated on a hillside at the former home of Taliban leader Mohammad Omar — as part of the agency-run paramilitary group called the Kandahar Strike Force.

These relatives, who spoke on the condition of anonymity, said Mohammad was not a member of the strike force, which Karzai helped recruit to fight the Taliban, but that he shared intelligence with U.S. officials and arrested hundreds of insurgents over the years.

“If there was something Sardar could do that the Americans couldn’t, they would ask him to do it,” Malik said. “If American forces were suspicious of someone, they were asking Sardar to make the arrest.”

On the morning of the killing, Mohammad walked into Karzai’s bustling home, asked for a private moment, and showed him a document listing the names of men who worked for him. As Karzai looked at it, Mohammad pulled out a pistol and shot him. One bullet struck the right side of his face and exited behind his ear; another hit near his heart, according to his death certificate. He died before he reached nearby Mirwais Hospital; while there, a doctor said, someone stole his watch.

After the shooting, Karzai’s guards entered the room and riddled Mohammad with bullets — his death certificate said he was shot in the skull and had 11 other gunshot wounds. Mohammad’s body was taken into the streets and strung up from a building by a rope, before eventually arriving at the hospital. Despite Islamic custom demanding a swift burial, on Thursday morning Mohammad’s corpse was still in the hospital’s refrigerated morgue in a white body bag. Nobody has come to retrieve it and the relatives said they are waiting for it to be delivered.

“We feel sorry for both of them,” said one relative. “We don’t know what caused this killing.”

The families were still so close, he said, that he helped dig Ahmed Wali Karzai’s grave.

Special correspondent Javed Hamdard contributed to this report.